I am assuming this needs to be relocated outside the unit and also I need to add moisture barrier to the foundation/floor etc.It's my understanding that a regular designer cannot help with this and I will have to engage a specialist to help with this.

That said, I focus on a very different market segment (mostly 800k to 1.5 mm on the residential side) so that dictates how I approach things.Water issues are the number one cause of litigation in my line of work so I am very focused on water/moisture management. 

Is this a normal thing with moisture trapped under the laminate padding?

They can look for recent damage and do moisture tests.  

In addition to new vents we are also considering installing cedar planks on all three bathroom ceilings because it’s mold resistant and (hopefully) handles moisture better than paint.Does anyone have experience with this?

A whole property humidifier requires maintenance, is prone to repairs and increases risk of mold through higher levels of moisture.

Fill the cavity with insulation (like Roxul Safe and Sound and be diligent about sealing any penetrations around electrical boxes with sound-deadening putty.

Additionally, there is evidence at a number of windows of moisture penetration.

Congrats on your first Rental, I too am looking to penetrate the Idaho Real Estate Investment Market.

A quick question here, when I am building a new bathroom with a shower do I need to apply the redgard material or just the purple or green moisture resistant Sheetrock is enough?